There are 3 objectives of the proposed research: (1) to develop an isotopic marker of bowel infarction which will permit earlier diagnosis; (2) to study a variety of vasodilators to determine which is optimal for reversing vasoconstriction of the mesenteric circulation associated with non-occlusive mesenteric ischemia of cardiac origin; and (3) to use our observations from these experiments to formulate improved diagnostic approaches and treatment plans for patients with non-occlusive mesenteric ischemia. During the first year of the project, a technique for imaging experimental canine bowel infarction with intraarterial or intravenous 99m Technetium Pyrophosphate was developed. We confirmed that the technique was not useful for the detection of ischemia but instead widespread infarction needed to be present for positive images. In the second year, we developed a highly sensitive radionuclide test for imaging experimental nonocclusive ischemia. We also evaluated other radionuclide techniques in order to determine their mechanisms for radiopharmaceutical uptake. In addition, we developed a reproducible and reliable canine model of nonocclusive mesenteric ischemia based on cardiac tamponade. Our current work will be directed towards evaluating various vasodilators in reversing ischemia in our animal model. We will also evaluate the new radionuclide technique in our model to determine its clinical application. Results from this work should provide a direct means to alter the poor prognosis of nonocclusive mesenteric ichemia in patients by providing a rational approach to its diagnosis and treatment.